Actually, I think you are correct in your approach. The Reggae players most certainly lower the treble to remove muchhe finger sound but there are different types of Reggae bass.
The Bob Marly stuff is an older style of Reggae bass sound, pre Hip Hop and not electronic. On some newer Reggae stuff they use synths to get a very low, deep sound. Those that use basses obviously turn the treble down either with the tone control or on the board. I would suggest recording the instrument in a more falt range and useing the best EQ you can get your hands on to get the sound.
Another important factor in bass sound is the strings. You should record with fresh strings if possible and you should check out different types of strings and their charactersitics and sound. Since you know the sound you want, if you have a good music store near you they should be able to help. Otherwise, check out the web sites of manufacturers and see what they say.
One last suggestion is there are boxes that will give you extra and deeper bass. Some are pedal that produce the tone an octave lower though your would not necessarily want the top note, just the bottom. Whether or not this would work is up to your ingenuity. Then there is a dbx box that produces lower bass (I believe) and a few others. Aphex now makes a pedal that might do this. They have a bass boost type device on their recent Aural Exciter and I believe a cheaper pedal version of it.
I would not strongly recommend those boxes since simply using the right strings and adjusting the EQ will give the best result.
Something that took me a while to get used to was the monitoring of bass. Of all the instruments, bass seems to me to change most dramatically from one monitor to the next. If you are monitoring on near field speakers without a sub-bass speaker, you might not be hearing all of the lower bass that is recorded. Thus if you add too much, when you do hear the mix on a more full range speaker, there will be too much bass and it will tend to be boomy.
I also think that some of the more recent Reggae tracks might use a mixture of different bass sounds. I have experimented with this and found it to be pretty good. I can get the real low, deep sound and still have definition by mixing in a more straigh forward sounding bass. The real low, deep, treble almost off sounds tend to have little definition and be weak on the attack. By doubling the bass part with a regular bass sound your get the right mix of attack and bottom.
By the way, I have read interview with many engineers that roll off some treble from the bass no matter what styl of music they are recording to eliminate fret noise, buzzing and the like. It tends to make the bass sound tighter.
Finally, there are no rules in how to make the sound and I am sure that Reggae musicians experiment and use various techniques including direct boxes, amplifiers, different microphones etc. The main thing is to know what sound you want to hear and get it any way you can. If it sounds right, it is right.